Synthese einfachster Polymethinfarbstoffe

CASPT2 calculation of the excited states of symmetric polyenyl cations

“…In streptocyanine dyes, however, the data are known. 38,39 In these compounds the bathochromic shift due to methyl substitution is between 10 and 55 nm for systems with 6 to 12 p-electrons which is significantly smaller than the shift calculated for the polyenyl cations.…”

Energy Spectra and Electric and Magnetic Properties of 1D Stacks of Conjugated π-Electron Systems with Defect Surface States. I. π Systems with Tamm Surface States

“… a Calculated values of the longest-wavelength transition of noninteracting molecules (monomers). b Experimental values of the longest-wavelength transition of noninteracting molecules (monomers). , c Calculated transition energy of the J aggregate (best agreement with the experimental value). d Experimental values of the transition energies of J aggregates (Δ E ( J )). , …”

“…In Figure , the polymethine cyanines forming the stacks for which the excitation energies were calculated are shown. The interplanar distance, R , between the planes of neighboring monomers varies between 3.3 and 3.7 Å. ,, The calculations have been carried out with different values of the distance R .…”

Relationships between basicity, structure, chemical shift and the charge distribution in resonance-stabilized iminoaminesElectronic supplementary information (ESI) available: energies and N⋯N distances in geometry-optimised iminoamine bases. See http://www.rsc.org/suppdata/p2/b2/b200899h/

“…There is evidence for increased resonance (less localization of electrons in alternant single and double bonds) in the unprotonated iminoamine bases, when one looks at the length of the imino function's N᎐ ᎐ C bond: it has the value of 1.281 Å in G [1]; increases to 1.288 Å in G[3]-G [11] and is still longer in all other species, reaching a maximum value of 1.302 Å in G [5](30) (12). Optimized H 2 C᎐ ᎐ NH has a bond length of 1.272 Å at the same level of theory, i.e.…”

“…6, 7 More recently, an extensive synthetic programme has been undertaken by Isobe et al to prepare chiral superbases based on the guanidine motif, with a view to applications in asymmetric synthesis. [8][9][10] The prototype unbranched amidine formamidine H 2 N-CH᎐ ᎐ NH is known, 11 as are the analogous extended conjugated chain aminines H 2 N-(CH᎐ ᎐ CH) n -CH᎐ ᎐ NH n = 1 and 3. 11, 12 Formamidine is not particularly basic, but it will be shown in this work that extending the conjugated carbon chain backbone has a very marked effect on the gas-phase basicity.…”